Universal tap-off box with a latch mechanism

ABSTRACT

A tap-off box includes a latch that automatically secures the tap-off box to a busway upon insertion of a mast into the busway. The latch is in the form of a single spring-loaded member that latches onto a rail as the masthead is pushed into the busway. A push button actuated camming member pushes the latch away from the rail to enable the masthead to be withdrawn from the busway. The push button and camming member are independent of the mechanism that extends and retracts the contacts while the masthead is inserted and latched into the busway. The tap-off box may also include non-contact current monitoring sensors with voltage sensing inserts that an auxiliary breaker switch in applications other than a tap-off box, and an infrared emitting faceplate that can be adapted for monitoring a variety of breakers from outside the tap-off box.

BACKGROUND OF THE INVENTION 1. Field of the Invention

This invention relates to a system for distributing electrical powerfrom a junction box to electrical devices via conductors installed in apower track, referred to herein as a busway. More particularly, theinvention relates to distribution sub-assemblies or power taps, referredto herein as tap-off boxes, that may be removably connected to thebusway or track at arbitrary locations without shutting down the powersupply.

The tap-off boxes of the invention include a number of improvements,including the addition of a mechanism for automatically latching thetap-off box to the busway, current transformer (CT) sensor assembliesthat detect breaker status in addition to monitoring currentsdistributed via the tap-off box, and replaceable faceplates that permitthermal scanning of internal components from outside the tap-off box.

A preferred embodiment of the tap-off box includes optional butadvantageous features that allow the sub-assemblies or power taps to beadapted to or configured for a wide variety of busway applications andelectrical device requirements, so that the tap-off box may be referredto as a “universal” tap-off box.

The invention also relates to an improved CT sensor that detectstripping of a breaker, in addition to monitoring currents, and that maybe used in a power distribution sub-assembly or power tap for a buswayor track, as well as in other current-sensing applications.

2. Description of Related Art

The rigorous demands of mission critical data center sites requiremethods to quickly disconnect and reconnect equipment without removingpower from any other equipment. Additionally, all power distributionsystems of the type used in mission critical data centers and othersites requiring continuous power distribution to multiple devices mustbe capable of providing monitoring of power parameters both locally andremotely. An example of such a power distribution system is disclosed inU.S. Pat. No. 7,819,676, assigned to Power Distribution, Inc. andincorporated herein by reference.

FIG. 1 is a perspective view of a section of the power track or buswayillustrated in U.S. Pat. No. 7,819,676. The busway is made up of a powertrack housing assembly that supports isolated high current conductors. Acommercial version of the illustrated busway is sold by PowerDistribution, Inc. as part of the POWERWAVE™ and POWERWAVE 2™ bussystems. As illustrated in FIG. 1, the busway housing assembly includesa housing or enclosure 1; insulators 2; the high current conductors orbus bars 3; and auxiliary sub-channels 9 that may contain communicationscomponents, such as data signal-carrying electrical or fiber opticcommunications cable 7 and data connectors 4 for connecting the cable tomonitoring circuitry in the individual tap-off boxes, and/or an isolatedground conductor for engaging a corresponding ground element (not shown)extending from the tap-off box. Housing or enclosure 1 may furtherinclude grooved runways 6 extending along the top and sides of thehousing assembly for mounting or securing electromagnetic interference(EMI) shielding and/or mounting plates (not shown) that enable thebusway to be secured to a ceiling or overhead mounting structure.

It will be appreciated that the present invention may be applied to orused with busway systems other than the one disclosed in U.S. Pat. No.7,819,676, or the PowerWave™ bus systems, and that features of thetap-off box may be varied to accommodate the different bus systemswithout departing from the scope of the invention. On the other hand, itis to be understood that the preferred embodiment of the inventionshares features with the PowerWave™ bus system, including springcontacts that engage the conductors or bus bars 3, and a spring contactcamming mechanism that is activated, as described below, by a slidableand rotatable knob.

One of the improvements offered by the present invention relates tosecuring of the tap-off box to the busway, and in particular to alatching mechanism that is independent of the contact-engagementmechanism, and that automatically latches the tap-off box in placebefore the camming mechanism is activated to cause the spring contactsto engage respective conductors in the busway. The inclusion of anindependent latching mechanism ensures that the tap-off box is properlypositioned at the time the contacts are engaged so as to ensure a properconnection and avoid damaging the contacts, while also preventing thetap-off box from being unintentionally pulled from the busway while thecontacts are engaged, which could cause damage to the contacts or buswayand present a serious safety hazard.

Unlike known tap-off box latching mechanisms, the latching mechanism ofthe invention does not require a complex interlock with thecontact-engaging mechanism, and furthermore does not require any actionon the part of the installer other than insertion of the tap-off boxcontact mast into the busway. In contrast, prior tap-off boxarrangements having independent latching mechanisms, such as the onesdisclosed in U.S. Pat. No. 3,611,252 and German Publication No.DE102010036081, have required some sort of manual intervention on thepart of the installer to secure the tap-off box after the mast has beeninserted into the track or busway.

For example, the tap-off box securing mechanism of U.S. Pat. No.3,611,252 uses a spring-biased member that automatically extends into aslot only after a mast of the tap-off box has been inserted into thetrack and the tap-off box and mast have been rotated into a finalcontact-engaging position. In this arrangement, a spring-biased blockingmember prevents rotation of the tap-off box back to a position at whichit can be removed. On the other hand, the tap-off box latching mechanismdisclosed in German Patent Publication No. DE102010036081 providespositive latching of a tap-off box upon purely linear insertion of acontact assembly into the track, without any rotation, but requires acomplex “connecting mechanism” consisting of dual axially opposedspring-biased “connecting elements” that snap-on to latch the tap offbox to the rail by engagement between bearing surfaces on the connectingelements and abutment surfaces on the rail, and further requires anadditional “locking mechanism” operated by a handle in order to bothinitially prevent movement of the locking elements in a disengagingdirection, and also to move the locking elements in a disengagingdirection.

Other examples of non-automatic tap-off box latching mechanisms includethose disclosed in U.S. Pat. No. 7,744,386 and PCT Patent PublicationNos. WO 94/24731 and WO 97/00167, in which the latch and contacts areactuated and withdrawn together by a common switch or lever; U.S. Pat.No. 9,379,502, which discloses a latching mechanism operatedindependently from the contact engaging/disengaging mechanism, but inwhich the latching mechanism is still lever-operated in both thelatching and unlatching directions; and U.S. Pat. No. 3,686,614, whichdiscloses a latching mechanism that is lever-operated to move a latchingmember in the latching direction, against a spring bias in theunlatching direction (which is operated the direction needed to achieveautomatic latching).

Finally, by way of further background, non-automatic tap-off boxsecuring mechanisms or means that are neither automatic actuated bylevers, cam, or the like include those of PCT Publication No.WO2012/032381, which describes a tap off box latching arrangementactuated by a cover interlock; U.S. Pat. No. 2,861,139, which disclosesa cover-operated interlock for the contacts only, and in which thetap-off box is secured to the bus by screws; U.S. Pat. No. 2,984,769,which discloses a tap off-box with cover-contact interlock that issimply hung from the busway by hooks; and U.S. Pat. No. 2,888,529, whichdiscloses a cover-operated interlock between a load switch and thecontacts.

Another improvement offered by the present invention relates tomonitoring of current in a branch circuit carried by the tap-off box,and in particular to the use of a new type of non-contact current sensorin which is installed a plastic or graphite voltage-sensing insert thatprovides an anchor for the current sensor and that replaces an auxiliarycircuit breaker trip detection switch to detect tripping of a respectivecircuit breaker in the corresponding branch circuit.

It is known to use arrays of current transformer (CT) sensor componentsto non-invasively monitor current in branch circuits, both in connectionwith a breaker panel board and also in a tap-off box. Such CT sensorarrays are disclosed, for example, in U.S. Pat. Nos. 8,421,443 and6,809,509. Other conventional CT sensor arrays and housingconfigurations are disclosed in U.S. Patent Publication Nos.2014/0210453; 2014/0167787; and 2005/0162252, and U.S. Pat. Nos.9,146,259; 8,680,845; 8,421,443; 7,652,871; 7,477,058; and 6,329,810. Ofthese, U.S. Pat. No. 8,421,443 is of interest because the CT sensorassembly an additional component, in the form of a memory chip 226,embedded in the individual transformer housing. However, none of theconventional current sensors have a way to detect whether an absence ofcurrent is caused by a tripped circuit breaker or just normal operationof the branch circuit. Instead, it has heretofore been necessary toprovide an auxiliary circuit breaker trip detection switch operated bythe movable contact arm assembly of the breaker to detect whether acurrent interruption has been caused by tripping of the breaker. Whileeffective, the inclusion of auxiliary breaker trip detection switches ina multiple-breaker tap-off box, where space may be at a premium, isinconvenient and costly. Furthermore, each different type of breakerwill require a different auxiliary trip detection switch. Because thetrip detection switch is mechanically connected to the breaker, there isno way to provide a single auxiliary switch that can be used withmultiple circuit breaker configurations.

Another especially advantageous feature that may be provided in thetap-off box of the present invention is a replaceable faceplate made ofa material transparent to infrared radiation so as to permit infraredscanning of breakers from outside the tap-off box, and that may bereplaced by a different infrared radiation transparent faceplate toaccommodate different breaker configurations without having to replacethe entire cover. By way of background, Power Distribution, Inc.'s U.S.Pat. No. 7,819,676 discloses a cover made of infrared transmissivematerial to facilitate infrared scanning of internal components. (col.8, lines 19-22), but not with a variable configuration breaker faceplatefor diverse types of breakers.

SUMMARY OF THE INVENTION

It is accordingly an objective of the invention to provide an improvedtap-off box for a power distribution busway system.

It is also an objective the invention to provide an improved latchingarrangement for a tap-off box.

It is a further objective of the invention to provide an improvedcurrent sensor arrangement for a tap-off box.

It is yet another objective of the invention to provide an improved IRmonitoring faceplate arrangement for a tap-off box.

These objectives are achieved, according to one aspect of the invention,by a tap-off box that includes a latching mechanism that automaticallysecures the tap-off box to the busway upon insertion of a springcontact-carrying mast into the busway. Automatic latching of the tap-offbox enables the spring contacts to be safely moved by an installer intoengagement with conductors in the busway.

According to a preferred embodiment of the invention, the latch is inthe form of a single spring-loaded member that latches onto a rail asthe masthead is pushed into the busway. A push button actuated cammingmember pushes the latch away from the rail to enable the masthead to bewithdrawn from the busway. The push button and camming member areindependent of the mechanism that extends and retracts the springcontacts while the masthead is inserted and latched into the busway.

The objectives of the invention are also achieved by a tap-off box withcircuit breaker monitoring that does not require an auxiliary breakertrip detection switch or other space-occupying components, but rather isprovided by a voltage sensing insert that fits into the currentmonitoring CT sensors, and that can be used with any circuit breakerconfiguration. The voltage-sensing insert may also be used to replace anauxiliary breaker switch in applications other than a tap-off box.

Still further objectives of the invention are achieved by a tap-off boxwith a cover configured to include a replaceable infrared transmittingfaceplate that can be adapted for a variety of different breakerconfigurations. According to a preferred embodiment of the invention,the cover may also include a replaceable current monitoring module withbreaker status indicator lights.

These and other features of the present invention will become apparentfrom the following description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a conventional busway to which thetap-off box of a preferred embodiment of the present invention may beinstalled.

FIG. 2 is an isometric view, taken from the front, of a tap-off boxconstructed in accordance with the principles of a preferred embodimentof the present invention.

FIG. 3 is an isometric view, taken from the rear, of the tap-off box ofthe preferred embodiment.

FIG. 4 is an isometric view of a mast included in the tap-off box of thepreferred embodiment.

FIGS. 5 and 6 are side views showing operation of a latching mechanismas the tap-off box of the preferred embodiment is inserted into a buswayof the type illustrated in FIG. 1.

FIGS. 7 and 8 are side views showing variations of a latch member forthe latching mechanism illustrated in FIGS. 5 and 6.

FIG. 9 is an isometric view of the latch member illustrated in FIG. 8.

FIG. 10 is an isometric view of an unlatching mechanism for the latchingmechanism illustrated in FIGS. 5 and 6.

FIG. 11 is an isometric view, taken from the rear, showing furtherdetails of the mast of FIG. 4.

FIG. 12 is an isometric view, taken from the front, showing furtherdetails of the mast of FIG. 4 and latching/unlatching andcontact-engaging mechanisms for the tap-off box of the preferredembodiment.

FIG. 13 is an isometric view showing interior components of the tap-offbox of the preferred embodiment, with removed side and front panels.

FIG. 14 is an exploded view of the components shown in FIG. 13.

FIGS. 15a to 15d show parts of a laminated bus bar for use in thetap-off box of the preferred embodiment.

FIG. 16 is an isometric view of the tap-off box of the preferredembodiment, including side panels but with front and receptacle panelsremoved.

FIG. 17 is an isometric view corresponding to that of FIG. 16, with anadded receptacle externder.

FIG. 18 is an isometric view, taken from the rear, with an added coveradapter to allow increased enclosure depth.

FIGS. 19A and 19B are isometric views showing the tap-off box of thepreferred embodiment, with front panel removed, with and without sideand receptacle panels.

FIGS. 20 and 21 are isometric views showing alternative receptacle toppanel configurations for the tap-off box of the preferred embodiment.

FIGS. 22 and 23 are isometric views of the tap-off box of the preferredembodiment, including a variable configuration breaker faceplate.

FIG. 24 is an isometric view of the tap-off box of the preferredembodiment, showing a field replaceable monitoring unit.

FIG. 25 is an isometric view of the monitoring unit of FIG. 24.

FIG. 26 is an isometric view of the monitoring unit of FIG. 24, withcover removed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Throughout the following description and drawings, like referencenumbers/characters refer to like elements. It should be understood that,although specific exemplary embodiments are discussed herein there is nointent to limit the scope of present invention to such embodiments. Tothe contrary, it should be understood that the exemplary embodimentsdiscussed herein are for illustrative purposes, and that modified andalternative embodiments may be implemented without departing from thescope of the present invention.

FIGS. 2-12 show a latching mechanism and a contact-engaging mechanismfor a universal tap-off box according to a preferred embodiment of theinvention. The tap-off box includes a generally planar quadrilateralmast 11 that extends from a tap-off box housing 12. Mast 11 supportsfour spring contacts 13-16, two of which (13,14) are on a front side ofthe mast 11, as shown in FIG. 12, and two of which (15,16) are on therear side of the mast 11, as shown in FIG. 11. The spring contacts 13-16are positioned to engage conductors 3 on the two sides of a busway ofthe type illustrated in FIG. 1. Each of the contacts 13-16 is agenerally rectangular plate spring attached at one end 18 to the mast 11and having a distal, conductor-engaging edge 19 that rests against themast when a camming mechanism is in an initial position, and that iscammed away from the mast against a restoring force of the spring whenthe camming mechanism is rotated to a conductor-engaging position afterinsertion of the mast 11 into the busway. The spring restoring forcebiases the spring contacts 13-16 towards the mast 11.

The camming mechanism includes posts 20, each having a cam shapedcross-section in portions of the respective posts that extend behind thespring contacts 13-16. The posts 20 are rotatably secured to the mast byclips 21, and each post includes a cylindrical base 22 having a radiallyextending bore 23 for receiving a horizontal crank post 24 attached toslider 25, visible in an end view in FIGS. 5 and 6. Slider 25 is in turnattached to a knob 26 that is slidable along a horizontal guide slot 27near a top of the tap-off box housing 12.

In operation, the knob is initially on the left side as shown in FIG. 2.In this position, the posts 20 are in a position in which the springcontacts 13-16 rest against or are flush with the mast 11, allowinginsertion of the mast 11 into the busway. Following insertion of themast 11 into the busway, the knob 26 is slid to the right side of guideslot 27, moving the crank posts 24 to cause rotation of the cylindricalbases 22, which causes posts 20 to rotate. Rotation of the posts 20 camsthe distal conductor-engaging edges 19 of spring contacts 13-16 awayfrom the mast 11 and into engagement with the conductors 3 in thebusway. Knob 26 can then be rotated to cause it to clamp the housing 12of the tap-off box between the knob 26 and the slider 25, preventinglateral movement of the knob 26 and locking the spring contacts 13-16 inthe conductor-engaging position.

The configuration of the camming mechanism and spring contacts of thepreferred embodiment illustrated herein may be the same as configurationof the camming mechanism and contacts in the PowerWave™ systems sold byPower Distribution, Inc. However, those skilled in the art willappreciate that the camming mechanism and spring contacts may also bevaried without departing from the scope of the invention. Furthermore,unlike the conventional tap-off box connection system, the presentinvention adds an automatic latching arrangement that engages upon fullinsertion of the mast 11 into the busway, to hold the tap-off box inposition before the spring contacts are engaged, and to permit thespring contacts to be disengaged by manipulation of knob 26 while thetap-off box is still securely locked in position.

The latching mechanism of the present invention is best viewed in FIGS.5-12, and includes a single one-piece latch member 30 having a latchhead 31 with a busway engaging surface 32 and an inclined cam surface33, a main body with a pivot notch 34, a lower extension 35 with apushing surface 36, and a spring mounting slot 37 or integrated spring38. The pivot notch receives a pivot post 39 positioned in an opening 40in the mast 11, as shown in FIG. 4. The busway engaging surface 32 isarranged to engage a top surface 42 of one of the sub-channels 9 in thebusway of FIG. 1, but those skilled in the art will appreciate that thelatch head 31 and busway engaging surface 32 may be arranged to latchonto horizontal surfaces of a busway other than the illustrated surface,including surfaces not associate with sub-channels, depending on thedesign of the busway, and that the invention is not limited to use withthe busway of FIG. 1 or the particular latch member shape or structureillustrated in FIGS. 5-12. For example, the pivot notch 34 may bereplaced by a hole or by an axle extending from the latch member 30.

The latch member 30 is biased to pivot to the latching position by aseparate spring fitted into slot 37, or by the integrated spring 38.During insertion of the mast 11 into the busway, the inclined camsurface 33 first encounters a lower portion of the sub-channel 9, asshown in FIG. 5, or any structure between the latch head 31 and thelatch-engaging top surface 42. The latch member 30 is then caused topivot around post 39, against the force of the spring bias, until themast 11 is inserted into the busway by an amount sufficient to enablethe latch head 31 to clear the sub-channel 9 or other structure, asshown in FIG. 6, at which time the latch pivots in response to thespring bias and automatically engages the top surface 42 to latch themast 11 within the busway and prevent removal of the tap-off box. Atthis time, the spring contacts 13-16 are positioned to face conductors3, and may be safely moved into engagement with the conductors bymanipulation of knob 26, as described above. In addition, completion ofmast insertion results in independent ground springs 44, if provided,being positioned within corresponding slots in the busway, and rails 46,which extend from the top of the tap-off box, having engaged the buswayhousing 1.

While engagement of the latching mechanism is automatic, disengagementis provided by an unlatching mechanism that includes an unlatchingmember 47 having an elongated main body 471 from which extends a centralpusher 48 for engaging the pushing surface 36 of the latch member 30,integral or attached springs 49 for biasing the unlatching member 47 toa position in which the pusher 48 is disengaged from the pushing surface36, and buttons 50 for causing the unlatching member 47 to move againstthe spring bias and cause the pusher 48 to engage the pushing surface36. Further movement of the pusher 48 and pushing surface 36 in responseto pushing of buttons 50 then causes the latch member 30 to pivotagainst its own spring bias, and busway engaging surface 32 to disengagefrom top surface 42 so that the tap off box can be removed from thebusway. The use of two buttons 50 at opposite sides of the pushingmember forces the operator to firmly grasp the tap off box by, forexample, placing the operator's fingers on a surface of the housing 12opposite the surface from which the buttons extend, on both sides of thebox, and to simultaneously push on both buttons 50 by using theoperator's thumbs in order to move the pusher 48 far enough to causedisengagement, thereby preventing premature or unintentional unlatchingof the tap-off box and ensuring that the operator's hands are in aposition to safely remove the tap off box by pulling vertically on bothsides of the housing 12.

FIGS. 13 and 14 show the interior of the tap-off box of the preferredembodiment, which the front and sides of the housing removed. Housing 12contains power distribution and monitoring circuitry, including circuitbreakers, bus bars, and current sensors, as will be described below.

Each of the spring contacts 13-16 is electrical connected by respectivewires (not shown) that extend through the mast to terminals 54positioned near a top of the tap-off box. Terminals 54 are connected tothe circuit breakers 55 by a laminated bus system 56 made up of fourplates 57-60 shown respectively in FIGS. 15a to 15d , which distributethe current supplied through the four spring contacts 13-16 andcorresponding terminals 54 into two branch circuits. Parts 57-60 are inthe form of conductive plates with appropriately positioned terminalsand laminated together with insulation layers to form a unitary assemblythat can easily be installed in the tap-off box as a unit, and that canbe customized for different circuit breaker and branch circuitconfigurations by forming the plates 57-60 to have appropriatelypositioned terminals. It will be appreciated that the circuit andcircuit breaker configurations, including the number of spring contactsand bus conductors, and the number of branch circuits, may be variedwithout departing from the scope of the invention. To this end, the useof the laminated bus assembly, which is preferred but not required,makes it possible to more easily vary the branch circuit configuration.Furthermore, in order to better accommodate different types of breakersor breakers with different current capacities, the breakers 55 areoptionally mounted on an adjustable height mounting bracket 61.

The downstream sides of the circuit breakers 55 and ground terminals 62are connected by wires (not shown) to output connectors or receptacles63,64 having selected alternative configurations, as will be describedbelow. in connection with FIGS. 20 and 21. The wires extend inconventional fashion through respective central openings 651, 661 incurrent sensors 65,66, which are connected to a field replaceablemonitoring module 71 via respective printed circuit boards 67,68 and aninterposer printed circuit board 69 containing an output connector 70.The monitoring module 71 contains circuitry for providing an outputmonitoring signal via a communications cable 72 that can, for example,be attached to a databus carried by one of the channels 9 in the busway.Those skilled in the art will appreciate that monitoring module 71 andcommunications cable 72 may be replaced by a different format module andconnector as desired. The interposer printed circuit board 69 ispreferably positioned above sensor circuit boards 67,68 to save space,with connection between the circuit boards being provided by one or morejumpers or ribbon cables 73. It will be appreciated that theconfiguration of the respective circuit boards 67-69, output connector70, monitoring module 71, and related components may be varied withoutdeparting from the scope of the invention.

As illustrated in FIGS. 13 and 14, the current sensors 65,66 arenon-contact, single phase CT current sensors that surround the branchcircuit connection wires extending between the output receptacles andthe circuit breakers 55. Such sensors are typically made up of wirewound toroidal coils on a metallic or nonmetallic core and enclosedwithin a plastic housing that may be mounted to the circuit board andelectrically connected via terminals connected to the toroidal coils,and are commercially available. As a result, the sensors 65,66 may befreely varied without departing from the scope of the invention, exceptto the extent that the current sensors 65, 66 are capable of receivingvoltage sensing inserts 74.

The voltage sensing inserts 74 replace the auxiliary breaker switchescommonly used to detect tripping of the breaker based on breaker contactpositions, and may be made up of a generally annular, plastic orgraphite encased non-contact voltage sensor element that may bepositioned on the printed circuit board 67 adjacent respectivenon-contact current sensors 65 to detect voltages in wires passingthrough the central openings 651 of the current sensors 65. As is wellknown, non-contact voltage sensing elements may take a variety of forms,such as a capacitive plate or wire (not shown). In order to detecttripping of the breaker, the voltage sensing elements are arranged tooutput a signal upon detecting a change in voltage that results when thebreaker goes from a closed position to an open position. Rather thanbeing connected to the current monitor, the signal-outputs of the insertare connected to monitoring and indicator circuitry that would otherwisebe connected to the auxiliary switch. The auxiliary switch monitoringcircuitry may, for example, control breaker operation indicator lights75 on the monitoring module 71, as shown in FIG. 25. Monitoring module71 preferably further includes a blind connector 76, shown in FIG. 26,for connection to the output connector 70 of the monitoring module,which is situated on the interposer printed circuit board 69.

FIG. 16 shows a side plate arrangement for the tap-off box housing 12 ofthe preferred embodiment. The side plates 82 illustrated in FIG. 16 areextruded aluminum panels that provide enclosure rigidity and strength aswell as grounding continuity, and that are arranged to fit within aflange 83 of a back panel 84. By varying the width of the side plates82, top panel or cover 90 (see FIGS. 2, 22, and 23), and a receptaclepanel 85 (shown in FIG. 19B), the thickness of the tap off box may bevaried to accommodate different size receptacles 63,64 and/or breakers55.

The receptacle panel 85 shown in FIG. 19B fits within slots 86 formed inthe side plates 82 to ensure electrical ground continuity, and includeopenings 87 of various shapes to accommodate different sizes or types ofreceptacles such as, by way of example and not limitation, the IECversion receptacles 63 shown in FIG. 20 and the NEMA version receptacles64 shown in FIG. 21.

Those skilled in the art will appreciate that it is also within thescope of the invention to provide side panel or receptacle arrangementsother than the illustrated arrangements, including arrangements in whichthe top, side, and bottom panels or plates are integral with the back orfront panels, or formed in one piece therewith, and arrangements inwhich the receptacles are provided with adapters or extenders 88 toleave more room within the enclosure for bigger wires or cables. It isalso possible, as shown in FIGS. 20 and 21, to provide one or morepanels with an adapter such as the cover adapter 89 to increase thewidth to match the width of other panels or plates and allow increasedenclosure depth.

As shown in FIGS. 22 and 23, the front panel or cover 90 preferablyincludes not only an opening 91 for the output connector 70 and a recess92 for the monitoring module 71, but also an opening 93 for receiving afield replaceable breaker faceplate 94. The field replaceable breakerfaceplate 94 may have various configurations to accommodate differenttypes of breakers, and includes a plate 95 that is transparent toinfrared radiation to enable infrared scanning of the breakers fromoutside the tap-off box, without having to remove the front panel orcover 90.

Finally, as shown in FIG. 24, the monitoring module 71 may optionallyalso include one or more additional light emitting diode (LED) indicatorlights 96 to, for example, provide an indication that maintenance isrequired. To facilitate replacement of the faceplate 94, the recess 92may include posts 97 for receiving captive quarter turn fasteners 98 orsimilar fastening members. In addition, an adapter 99 may be provided toenable connection of the illustrated jack 100 with a Molex typemicro-fit connector provided in the busway. Those skilled in the artwill appreciate that the monitoring unit may use any of a variety ofdifferent communications protocols and jacks or adapters withoutdeparting from the scope of the invention.

What is claimed is:
 1. A tap-off box distributing power from a busway ofan electrical power distribution system, the tap-off box comprising: ahousing including power distribution and monitoring components; a mastthat extends from the housing and includes a plurality of electricalcontacts for engagement with respective conductors in the busway; and asnap-on latching mechanism that includes a spring-biased latch memberpivotally attached to the mast, wherein the latch member has a buswayengaging surface that engages an upper surface of a structure in thebusway, the latch member further including an inclined cam surface thatengages a lower surface of the busway structure and causes the latchmember to pivot in a first direction as the mast is inserted into thebusway, the latch member being moved in a second direction by thespring-bias into a latching position in which the horizontal engagingsurface engages the upper surface of the busway structure to latch thetap-off box into the busway after the latch member has moved past thebusway structure upon full insertion of the mast into the busway; and anunlatching mechanism positioned adjacent the latch member to engage andpivot the latch member in said first direction upon actuation by aninstaller to enable removal of the tap off box from the busway.
 2. Thetap-off box as claimed in claim 1, wherein the spring-bias is providedby a spring that is integral with the latch member.
 3. The tap-off boxas claimed in claim 1, wherein the spring-bias is provided by a platespring inserted into a slot in the latch member.
 4. The tap-off box asclaimed in claim 1, wherein the unlatching mechanism includes anunlatching member having a pusher, and the latch member includes a lowersurface engageable with the pusher to cause pivoting of the latch memberupon being engaged and pushed by the unlatching member towards the latchmember.
 5. The tap-off box as claimed in claim 4, wherein the unlatchingmember includes an elongated main body having said pusher extension at acenter and buttons at opposite ends, wherein pushing on the buttonscauses the unlatching member to move towards the latch member and causethe latch member to pivot in the first direction.
 6. The tap-off box asclaimed in claim 1, wherein the electrical contacts are spring contactsattached at one end to the mast, and further comprising a contactengaging mechanism that includes a plurality of camming posts rotatablymounted in the mast and positioned such that cam surfaces of the cammingposts are adjacent respective spring contacts, wherein when the cammingposts are rotated, the spring contacts are cammed by the cammingsurfaces into engagement with the conductors.
 7. The tap-off box asclaimed in claim 6, wherein the camming posts are actuated by a slidableknob and wherein the slidable knob is rotatable to lock the electricalcontacts in an engagement position.
 8. The tap-off box as claimed inclaim 1, wherein the power distribution and monitoring componentsinclude: circuit breakers configured to be electrically connected to theelectrical contacts and to output receptacles of the tap off box; andnon-contact current monitoring sensors, each having a central openingand positioned between the circuit breakers and the output receptaclesof the tap-off box.
 9. The tap-off box as claimed in claim 8, furthercomprising a voltage sensing insert installed in the central opening ofat least one of the non-contact current monitoring sensors, the voltagesensing insert including an annular voltage-sensing section that alsosurrounds the respective individual wire that passes through the atleast one non-contact current monitoring sensor, wherein the at leastone non-contact current monitoring sensor is installed on a firstcircuit board and the voltage sensing insert is electrically connectedto a circuit that detects a status of the circuit breaker based ondetection by the voltage sensing insert of an open or closed circuitcondition.
 10. The tap-off box as claimed in claim 9, further comprisinga monitoring module that includes at least one LED viewable from anexterior of the housing for indicating a status of the circuit breakeras detected by the voltage sensing insert.
 11. The tap-off box asclaimed in claim 10, further comprising an interposer circuit boardconnected by a ribbon cable to the first circuit board, the interposercircuit board including a first connector arranged to be connected to asecond connector in the monitoring module, the monitoring module beingremovably secured to a front panel of the tap-off box.
 12. The tap-offbox as claimed in claim 11, wherein the housing further includes arecess for removably receiving a current monitoring module.
 13. Thetap-off box as claimed in claim 11, wherein the housing includes a rearpanel, a top plate from which the mast extends, a pair of side plates, areceptacle panel, and a front panel, and the side plates are replaceableby side plates of a different thickness to accommodate circuit breakershaving different sizes.
 14. The tap-off box as claimed in claim 11,wherein the housing includes a rear panel, a top plate from which themast extends, a pair of side plates, a receptacle panel, and a frontpanel, and the receptacle panel is replaceable to accommodate differenttypes of receptacles.
 15. The tap-off box as claimed in claim 1, whereinthe housing includes a rear panel, a top plate from which the mastextends, a pair of side plates, a receptacle panel, and a front panel,the front panel including an opening arranged to receive a variableconfiguration breaker faceplate made of a plastic material that allowsIR scanning of circuit breakers within the housing.
 16. A non-contactcurrent monitoring assembly, comprising: a non-contact current sensorincluding a toroidal winding that extends around a central opening forsensing a current in a wire passing through the central opening; and avoltage sensing insert positioned adjacent to the non-contact currentsensor for detecting an open circuit condition of a circuit breakerconnected to the wire, wherein the circuit breaker lacks an auxiliarybreaker switch to detect tripping of the circuit breaker, tripping ofthe circuit breaker instead being detected based on an absence ofvoltage sensed by a voltage sensing insert in said wire passing throughthe central opening of the non-contact current sensor.
 17. A tap-offbox, comprising: a housing that encloses power distribution andmonitoring circuitry, wherein the housing includes a back panel, a topplate from which an electrical contact supporting mast extends, a pairof side plates, a receptacle panel, and a front panel, the front panelincluding an opening arranged to removably receive a variableconfiguration breaker faceplate made of a plastic material thattransmits infrared to enable infrared scanning of the power distributionand monitoring circuitry from outside the housing, the variableconfiguration breaker faceplate being removable and replaceable by adifferent variable configuration breaker faceplate to accommodatedifferent circuit breaker configurations.
 18. The tap-off box as claimedin claim 17, wherein the housing further includes a recess for removablyreceiving a current monitoring module.
 19. The tap-off box as claimed inclaim 17, wherein the side panels are replaceable by side panels of adifferent thickness to accommodate circuit breakers having differentsizes.
 20. The tap-off box as claimed in claim 17, wherein thereceptacle panel is replaceable to accommodate different types ofreceptacles.